Usefulness of bone metabolic markers in the diagnosis of bone metastasis from lung cancer

Development and validation of an early diagnosis model for bone metastasis in non-small cell lung cancer based on serological characteristics of the bone metastasis mechanism

Background

Bone metastasis significantly impact the prognosis of non-small cell lung cancer (NSCLC) patients, reducing their quality of life and shortening their survival. Currently, there are no effective tools for the diagnosis and risk assessment of early bone metastasis in NSCLC patients. This study employed machine learning to analyze serum indicators that are closely associated with bone metastasis, aiming to construct a model for the timely detection and prognostic evaluation of bone metastasis in NSCLC patients.

Methods

The derivation cohort consisted of 664 individuals with stage IV NSCLC, diagnosed between 2015 and 2018. The variables considered in this study included age, sex, and 18 specific serum indicators that have been linked to the occurrence of bone metastasis in NSCLC. Variable selection used multivariate logistic regression analysis and Lasso regression analysis. Six machine learning methods were utilized to develop a bone metastasis diagnostic model, assessed with Area Under the Curve (AUC), Decision Curve Analysis (DCA), sensitivity, specificity, and validation cohorts. External validation used 113 NSCLC patients from the Medical Alliance (2019-2020). Furthermore, a prospective validation study was conducted on a cohort of 316 patients (2019-2020) who were devoid of bone metastasis, and followed-up for at least two years to assess the predictive capabilities of this model. The model's prognostic value was evaluated using Kaplan-Meier survival curves.

Findings

Through variable selection, 11 serum indictors were identified as independent predictive factors for NSCLC bone metastasis. Six machine learning models were developed using age, sex, and these serum indicators. A random forest (RF) model demonstrated strong performance during the training and internal validation cohorts, achieving an AUC of 0.98 (95% CI 0.95-0.99) for internal validation. External validation further confirmed the RF model's effectiveness, yielding an AUC of 0.97 (95% CI 0.94-0.99). The calibration curves demonstrated a high level of concordance between the anticipated risk and the observed risk of the RF model. Prospective validation revealed that the RF model could predict the occurrence of bone metastasis approximately 10.27 ± 3.58 months in advance, according to the results of the SPECT. An online computing platform (https://bonemetastasis.shinyapps.io/shiny_cls_1model/) for this RF model is publicly available and free-to-use by doctors and patients.

Interpretation

This study innovatively employs age, gender, and 11 serological markers closely related to the mechanism of bone metastasis to construct an RF model, providing a reliable tool for the early screening and prognostic assessment of bone metastasis in NSCLC patients. However, as an exploratory study, the findings require further validation through large-scale, multicenter prospective studies.

Funding

This work is supported by the National Natural Science Foundation of China (NO.81974315); Shanghai Municipal Science and Technology Commission Medical Innovation Research Project (NO.20Y11903300); Shanghai Municipal Health Commission Health Industry Clinical Research Youth Program (NO.20204Y034).

N-telopeptide as a potential diagnostic and prognostic marker for bone metastasis in human cancers: A meta-analysis

Purpose

Whether N-telopeptide of type I collagen (NTx) can be applied for diagnosis and prognostic prediction of bone metastasis in human cancers is still conflicting. This study aimed to investigate the diagnostic and prognostic value of NTx for cancer patients with bone metastasis.

Methods

Embase, PubMed, Chinese National Knowledge Infrastructure and Wanfang databases were retrieved to collect related publications. In diagnostic meta-analysis, the sensitivity (SEN) and specificity (SPE) were calculated. Hazard ratio (HR) with 95% confidence interval (95% CI) was used in the prognostic meta-analysis. Sensitivity and publication analyses were conducted for potential heterogeneity sources.

Results

The pooled SEN and SPE were 77% (72-81%) and 80% (75-84%) for 45 diagnostic studies. A higher diagnostic efficacy was obtained from NTx combining with other markers (AUC: 0.94 (0.92-0.96)) for bone metastasis of human cancers, especially for lung cancer (AUC: 0.87 (0.84-0.90)), breast cancer (AUC: 0.83 (0.79-0.86)) and prostate cancer (AUC: 0.88 (0.85-0.90)) in Asian people (AUC: 0.86 (0.83-0.89)). For the value of NTx on prognosis of human cancers with bone metastasis, the pooled HR was 2.12 (1.74-2.58) for high versus low NTx level, indicating high NTx level would increase the risk of poor overall survival.

Conclusion

Our results indicated serum NTx combining with other markers can become a feasible biomarker for the diagnosis and prognosis prediction for bone metastasis of different cancers, including lung cancer, breast cancer and prostate cancer in Asian people.

Biomarkers for Prostate Cancer Bone Metastasis Detection and Prediction

Prostate cancer (PCa) causes deaths worldwide, ranking second after lung cancer. Bone metastasis (BM) frequently results from advanced PCa, affecting approximately 90% of patients, and it also often results in severe skeletal-related events. Traditional diagnostic methods for bone metastases, such as tissue biopsies and imaging, have substantial drawbacks. This article summarizes the significance of biomarkers in PCa accompanied with BM, including (1) bone formation markers like osteopontin (OPN), pro-collagen type I C-terminal pro-peptide (PICP), osteoprotegerin (OPG), pro-collagen type I N-terminal pro-peptide (PINP), alkaline phosphatase (ALP), and osteocalcin (OC); (2) bone resorption markers, including C-telopeptide of type I collagen (CTx), N-telopeptide of type I collagen (NTx), bone sialoprotein (BSP), tartrate-resistant acid phosphatase (TRACP), deoxypyridinoline (D-PYD), pyridoxine (PYD), and C-terminal pyridinoline cross-linked telopeptide of type I collagen (ICTP); (3) prostate-specific antigen (PSA); (4) neuroendocrine markers, such as chromogranin A (CgA), neuron-specific enolase (NSE), and pro-gastrin releasing peptide (ProGRP); (5) liquid biopsy markers, such as circulating tumor cells (CTCs), microRNA (miRNA), circulating tumor DNA (ctDNA), and cell-free DNA (cfDNA) and exosomes. In summary, some of these markers are already in widespread clinical use, while others still require further laboratory or clinical studies to validate their value for clinical application.

Predictive and Prognostic Biomarkers for Lung Cancer Bone Metastasis and Their Therapeutic Value

Lung cancer is the leading cause of cancer-related death worldwide. Bone metastasis, which usually accompanies severe skeletal-related events, is the most common site for tumor distant dissemination and detected in more than one-third of patients with advanced lung cancer. Biopsy and imaging play critical roles in the diagnosis of bone metastasis; however, these approaches are characterized by evident limitations. Recently, studies regarding potential biomarkers in the serum, urine, and tumor tissue, were performed to predict the bone metastases and prognosis in patients with lung cancer. In this review, we summarize the findings of recent clinical research studies on biomarkers detected in samples obtained from patients with lung cancer bone metastasis. These markers include the following: (1) bone resorption-associated markers, such as N-terminal telopeptide (NTx)/C-terminal telopeptide (CTx), C-terminal telopeptide of type I collagen (CTx-I), tartrate-resistant acid phosphatase isoform 5b (TRACP-5b), pyridinoline (PYD), and parathyroid hormone related peptide (PTHrP); (2) bone formation-associated markers, including total serum alkaline phosphatase (ALP)/bone specific alkaline phosphatase(BAP), osteopontin (OP), osteocalcin (OS), amino-terminal extension propeptide of type I procollagen/carboxy-terminal extension propeptide of type I procollagen (PICP/PINP); (3) signaling markers, including epidermal growth factor receptor/Kirsten rat sarcoma/anaplastic lymphoma kinase (EGFR/KRAS/ALK), receptor activator of nuclear factor κB ligand/receptor activator of nuclear factor κB/osteoprotegerin (RANKL/RANK/OPG), C-X-C motif chemokine ligand 12/C-X-C motif chemokine receptor 4 (CXCL12/CXCR4), complement component 5a receptor (C5AR); and (4) other potential markers, such as calcium sensing receptor (CASR), bone sialoprotein (BSP), bone morphogenetic protein 2 (BMP2), cytokeratin 19 fragment/carcinoembryonic antigen (CYFRA/CEA), tissue factor, cell-free DNA, long non-coding RNA, and microRNA. The prognostic value of these markers is also investigated. Furthermore, we listed some clinical trials targeting hotspot biomarkers in advanced lung cancer referring for their therapeutic effects.

Elevated N-telopeptide as a potential diagnostic marker for bone metastasis in lung cancer: A meta-analysis

BACKGROUND

Growing evidence indicates that the cross-linked N-telopeptide of type I collagen (NTx) is likely to be involved in the development of bone metastasis among lung cancer patients. We perform a meta-analysis to disclose the correlation between bone metastasis and NTx and also to evaluate its value in diagnosis of bone metastasis (BM) in lung cancer.

METHOD

Electronic databases were searched and calculated the weighted mean difference (WMD) with 95% confidence interval (CI) to assess the expression difference of NTx between BM+ and BM- lung cancer patients. Moreover, we conducted a sensitivity and specificity test and drew a summary receiver operating characteristic curve (SROC) to assess the diagnostic value of NTx in discerning bone metastasis.

RESULTS

A total of eleven studies with 1108 individuals were included in this analysis. The results showed an increased NTx was correlated with the incidence of lung cancer (P < 0.001). The overall sensitivity and specificity of serum NTx (sNTx) for discerning bone metastasis was 0.74 (95% CI = 0.67 to 0.79) and 0.85 (95% CI = 0.80 to 0.89), respectively. As for urine NTx (uNTx) the pooled sensitivity and specificity was 0.77(95% CI = 0.67 to 0.86) and 0.81(95% CI = 0.76 to 0.86). The area under the SROC curve was 0.8889(SE = 0.0255) and 0.8655(SE = 0.0254) for sNTx and uNTx respectively.

CONCLUSIONS

The elevation of NTx in lung cancer was positively related with the development and progression of bone metastasis. A higher specificity over sensitivity of NTx suggested that it is a more accurate biomarker to distinguish patients without bone metastasis. Regarding SROC curve, sNTx may be a better choice.

A meta-analysis survey of appropriate bone turnover markers in the detection of bone metastasis in lung cancer

BACKGROUND

A number of studies have investigated the clinical significance of bone turnover markers (BTMs) for the diagnosis of bone metastasis (BM) in lung cancer; however, they led to contradictory results. The aim of this meta-analysis was to investigate whether BTMs differ between lung cancer patients with and without BM.

METHODS

Articles were identified by searching Medline, Embase, Web of Science and Scopus. The studies that were identified were pooled and the weighted mean difference (WMD) and its corresponding 95% confidence interval (CI) were calculated. Subgroup analyses and publication bias detection were also conducted.

RESULTS

A final analysis of 1720 subjects (707 patients with BM and 1013 patients without BM) was performed from 16 cohort studies. From the pooled data in the meta-analysis, the total alkaline phosphatase (TALP) (104.35 U/l [95% CI 33.36-175.34]), bone-specific ALP (BALP) (13.24 μg/l [95% CI 8.50-17.98] or 6.84 U/l [95% CI 2.98-10.70]), C-terminal cross-linked telopeptide of type I collagen (ICTP) (5.07 μg/l [95% CI 3.58-6.56]) and N-terminal cross-linked telopeptide of type I collagen (NTX) (5.08 nM bone collagen equivalent/l [95% CI 2.82-7.33]) were significantly lower among BM patients than non-BM patients. Subgroup analyses detected that the serum level of tartrate-resistant acid phosphatase isoform 5b was significantly reduced in Caucasian patients with BM (-0.64 U/l [95% CI -1.02 to -0.25]), while increased in Asian patients with BM (2.69 U/l [95% CI 0.08-5.31]), compared to patients without BM.

CONCLUSIONS

The present meta-analysis suggested that serum measurement of TALP, BALP, ICTP and NTX might be helpful in detecting BM in lung cancer.

Bone turnover markers in serum and urine as diagnostic, prognostic and monitoring biomarkers of bone metastasis

Bone metastases are characterized by increased osteoblastic and/or osteolytic processes depending on the tumor type. The altogether destructive effect of metastasis formation promoted by increased metabolic activity raises the release of components from the osseous metabolism into the blood stream. These components are either enzymes directly involved in the alteration processes, metabolites/proteins that develop during this or bone matrix proteins released during this. These biomarkers are categorized in relation to their involvement in the bone formation or resorption as bone formation and resorption markers. Based on a PubMed literature search, a critical appraisal of the various biomarkers for diagnostic, prognostic, and monitoring purposes is given for patients with skeletal metastases caused by breast, prostate, lung, or renal cell carcinomas.

Response of Bone Resorption Markers to Aristolochia longa Intake by Algerian Breast Cancer Postmenopausal Women

Aristolochia longa is widely used in traditional medicine in Algeria to treat breast cancer. The aim of the present study was to investigate the response of bone resorption markers to A. longa intake by Algerian breast cancer postmenopausal women. According to the A. longa intake, breast cancer patients were grouped into A. longa group (Al) (n = 54) and non-A. longa group (non-Al) (n = 24). 32 women constituted the control group. Bone resorption markers (from urine) pyridinoline (PYD) and deoxypyridinoline (DPD) were determined by HPLC. Serum and urinary creatinine, uric acid, and urea were measured. 1 g of A. longa intake resulted in significant rise of renal serum markers and a pronounced increase of bone resorption markers. The intake of A. longa roots is detrimental for kidney function and resulted in high bone resorption, maybe due to the reduction in renal function caused by the aristolochic acids contained in the roots.

Clinical significance of serum BAP, TRACP 5b and ICTP as bone metabolic markers for bone metastasis screening in lung cancer patients

BACKGROUND

We investigated the clinical significance of serum bone-specific alkaline phosphatase (BAP), tartrate-resistant acid phosphatase isoform 5b (TRACP 5b) and type I collagen carboxyterminal telopeptide (ICTP) as bone metabolic markers for bone metastasis (BM) screening in lung cancer patients.

METHODS

Newly diagnosed advanced lung cancer patients with (N = 130) and without (N = 135) BM were enrolled in the study. Serum BAP, TRACP 5b and ICTP were measured before the treatment.

RESULTS

BAP, TRACP 5b and ICTP values were higher in patients with BM compared with patients without BM (all P < 0.0001). Area under ROC curve (AUC) of BAP, TRACP 5b and ICTP was 0.760, 0.753 and 0.835 (all P < 0.0001), respectively. The cut-off values for BAP, TRACP 5b and ICTP were 21.8 μg/l, 7.8 U/l and 8.8 μg/l, respectively. When TRACP 5b and ICTP were combined, AUC was elevated to 0.895 (P < 0.0001), and the cut-off values were TRACP 5b 7.6 U/l and ICTP 8.4 μg/l.

CONCLUSIONS

We conclude that serum BAP, TRACP 5b and ICTP may serve as useful tools for BM screening in lung cancer patients.

Osteopontin genetic variants are associated with overall survival in advanced non-small-cell lung cancer patients and bone metastasis

PURPOSE

Osteopontin (OPN) plays important roles in the modulation of apoptosis, angiogenesis, immune response, and tumor invasion. Elevated osteopontin expression has been reported in the lung cancer tissues compared to counterpart normal tissues. This study examined whether genetic variations in the osteopontin gene are associated with survival of lung cancer patients and occurrence rate of bone metastasis.

EXPERIMENTAL DESIGN

Three hundred and sixty patients with stages I to IV between 2003 and 2007 were recruited in this study and same number of healthy persons were used as control. Three promoter osteopontin polymorphisms, OPN-66 T/G, -156G/GG, and -443C/T variants were genotyped using DNA from blood lymphocytes. Chi-square test and a Fisher's exact test were used to analyze the genotype distribution among TNM stages and incidence of bone metastasis and lymph mode metastasis. Kaplan-Meier method and log-rank test were used to compare survival by different genotypes.

RESULTS

For the variant at nt -443 (CC), there was a significant difference between the number of patients with stage IV and those with all other stages of lung cancer (p < 0.01). Patients with -443 (CC) variant had significant higher incidence of bone metastasis development compared to other genotypes. For the variant at nt -443 (CT), there was a significant difference between the number of lung cancer patients with stage III + IV and those with stage I + II (P < 0.01). The survival rates for patients with the C/C genotype were significantly lower than for patients with the other two genotypes (C/T, T/T).

CONCLUSION

OSTEOPONTIN -443C/T polymorphism is a potential predictive marker of survival in lung cancer patients, it is correlated with bone metastasis significantly.

Markers of bone metastases in breast and lung cancers

AIM AND BACKGROUND

The aim of the present study was to evaluate correlations between serum osteocalcin, osteoprotegerin and NTX (Cross-linked N-telopeptides of Type I Collagen) and urinary NTX in breast and lung cancer patients with bone metastases. These four markers are considered to have important roles in bone formation, resorption and metastases.

METHODS

Four markers were determined in the sera of 60 breast cancer and 21 lung cancer patients and healthy controls (n=30). Serum levels were studied using ELISA and EIA.

RESULTS

The median levels of serum osteoprotegerin (p<0.001) and osteocalcin (p=0.003) were higher in patients. Significant correlations were observed between the serum NTX-osteocalcin (r=0.431; p<0.001), serum NTX- osteoprotegerin (r=0.42; p=0.003) and serum NTX - urine NTX (r=0.255; p=0.022).

CONCLUSION

We conclude that osteocalcin, osteoprotegerin and NTX are independent diagnostic tools. Due to the ease of urine collection, urine NTX may be applied routinely to allow early detection of bone metastases and indicate progression of the disease.

Experimental model of heterotopic ossification in Wistar rats

Heterotopic ossification (HO) is a metaplastic biological process in which there is newly formed bone in soft tissues adjacent to large joints, resulting in joint mobility deficit. In order to determine which treatment techniques are more appropriate for such condition, experimental models of induced heterotopic bone formation have been proposed using heterologous demineralized bone matrix implants and bone morphogenetic protein and other tissues. The objective of the present experimental study was to identify a reliable protocol to induce HO in Wistar rats, based on autologous bone marrow (BM) implantation, comparing 3 different BM volumes and based on literature evidence of this HO induction model in larger laboratory animals. Twelve male Wistar albino rats weighing 350/390 g were used. The animals were anesthetized for blood sampling before HO induction in order to quantify serum alkaline phosphatase (ALP). HO was induced by BM implantation in both quadriceps muscles of these animals, experimental group (EG). Thirty-five days after the induction, another blood sample was collected for ALP determination. The results showed a weight gain in the EG and no significant difference in ALP levels when comparing the periods before and after induction. Qualitative histological analysis confirmed the occurrence of heterotopic ossification in all 12 EG rats. In conclusion, the HO induction model was effective when 0.35 mL autologous BM was applied to the quadriceps of Wistar rats.

Diagnostic and prognostic use of bone turnover markers

The use of bone turnover markers in oncology includes monitoring of anticancer treatment in patients with malignant disease metastatic to the bones (therapeutic monitoring), predicting the risk of bone relapse in patients with a first diagnosis of potentially curative, early-stage malignant tumors (prognostic use), and making an early diagnosis of (microscopic) malignant bone disease in patients with a known malignant tumor to start early bone-targeted treatment and avoid skeletal-related events (diagnostic use). Concerning prognostic use, there is limited evidence for bone turnover markers to predict the occurrence of metachronous bone metastases in patients with early-stage malignant tumors, with serum PINP (N-terminal propeptide of procollagen type 1), ICTP (Carboxyterminal cross-linked telopeptide of type I collagen), bone sialoprotein (BSP), and tumor immunoexpression of BSP being the most promising candidates. Concerning diagnostic use, serum bone-specific alkaline phosphatise (BSAP), PINP and osteoprotegerin (OPG) were repeatedly shown to be associated with synchronous bone metastases in patients with breast or lung cancer, but sensitivity of these markers was too low to suggest that they might be preferred over conventional bone scans for the diagnosis of bone metastases. A somewhat higher sensitivity for the diagnosis of bone metastases was found for urinary NTx (N-terminal cross-linked telopeptide of type I collagen) and serum ICTP in solid tumor patients, serum TRAcP-5b (Tartrate-resistant acid phosphatase type 5b) in patients with breast cancer and serum BSAP, PINP and OPG in prostate cancer patients. Both prognostic and diagnostic use of bone turnover markers are reviewed in this chapter.

Prognostic significance of bone markers in patients with lung cancer metastatic to the skeleton: a review of published data

The presence of bone metastases significantly affects clinical outcome and quality of life parameters in patients with lung cancer. In this review, we aimed to evaluate the predictive value of markers of bone turnover in skeletal morbidity and clinical parameters, including disease-free survival (DFS) and overall survival (OS), in patients with lung cancer metastatic to the skeleton who were receiving bisphosphonate treatment. A comprehensive overview of all articles published from 1995 to date in 3 medical databases (PubMed, Scopus, and Cochrane) was performed using the keywords bone markers and lung cancer. Most bone formation markers (including bone alkaline phosphatase [bALP], osteocalcin [OC], and osteoprotegerin [OPG]), most bone absorption markers (including urinary calcium, osteopontin [OPN], receptor activator of nuclear factor κ-B ligand [RANKL], tartrate-resistant acid phosphatase isoform-5b [TRACP 5b]), and the metabolites of type I collagen had elevated concentrations in patients with lung cancer and bone metastases compared with patients without skeletal involvement. Two large studies showed that urinary N-terminal telopeptide (NTX) levels are a valid diagnostic method for early detection of bone metastases and a more consistent prognosticator than bALP. Treatment with zoledronic acid reduces NTX, TRACP-5b, RANKL, and OPG levels. Furthermore posttherapeutic reduction of urinary NTX levels seems to correlate with lower risk of skeletal-related events (SREs). Levels of markers of bone remodeling reflect the presence of bone metastases and may contribute to early detection of occult skeletal disease or monitor the effect of bisphosphonate treatment. However their ability to predict SREs, as well as DFS and OS, remains debatable.

Consensus on the utility of bone markers in the malignant bone disease setting

Biochemical markers of bone turnover provide insight into ongoing rates of skeletal metabolism and tumor-bone interactions in patients with malignant bone disease. This article reviews the available recent evidence assessing the potential of bone markers for detecting and monitoring malignant bone lesions in patients with advanced cancers, and for assessing overall skeletal health and response to antiresorptive therapies in patients at all stages of cancer progression. Most data thus far are for urinary N-terminal cross-linked telopeptide of type I collagen (NTX) in predicting risks of skeletal morbidity and death and monitoring response to zoledronic acid in patients with bone metastases. Ongoing studies are evaluating such correlations for other markers and therapies. Emerging evidence suggests that bone markers may help identify patients at high risk for bone metastasis or bone lesion progression, thereby allowing improved follow-up. Results from ongoing clinical trials evaluating such potential applications of bone markers are awaited.

The role of whole-body FDG PET/CT, Tc 99m MDP bone scintigraphy, and serum alkaline phosphatase in detecting bone metastasis in patients with newly diagnosed lung cancer

Bone scan (BS) and serum alkaline phosphatase (ALP) concentration are used to detect bone metastasis in malignancy, although whole-body fluoro-D-glucose positron emission tomography computed tomography (FDG PET/CT) is being used increasingly. But BS is still used for the detection of metastatic bone lesion. So we compared the usefulness of PET/CT, BS, and serum ALP in detecting bone metastases in patients with newly diagnosed lung cancer. The medical record database was queried to identify all patients with a new diagnosis of lung cancer between January 2004 and December 2005, who had a PET/CT, BS, and serum ALP before treatment. We retrospectively reviewed all patients' records and radiological reports. One hundred eighty-two patients met the inclusion criteria. Bone metastases were confirmed in 30 patients. The sensitivity values were 93.3% for PET/CT, 93.3% for BS, 26.7% for serum ALP concentration, and 26.7% for BS complemented with serum ALP concentration. The respective specificity values were 94.1%, 44.1%, 94.1%, and 97.3%. The kappa statistic suggested a poor agreement among the three modalities. FDG PET/CT and BS had similar sensitivity, but PET/CT had better specificity and accuracy than BS. PET/CT is more useful than BS for evaluating bone metastasis. However, in the advanced stage, because of its high specificity, BS complemented with serum ALP is a cost-effective modality to avoid having to use PET/CT.

Comparative characterization of pulmonary surfactant aggregates and alkaline phosphatase isozymes in human lung carcinoma tissue

Alkaline phosphatase (AP) isozymes are surfactant-associated proteins (SPs). Since several different AP isozymes have been detected in the pneumocytes of lung cancer patients, we attempted to identify the relationship between pulmonary surfactant aggregate subtypes and AP isozymes. Pulmonary surfactant aggregates were isolated from carcinoma and non-carcinoma tissues of patients with non-small cell carcinoma of the lung. Upon analysis, ultraheavy, heavy, and light surfactant aggregates were detected in the non-carcinoma tissues, but no ultraheavy surfactant aggregates were found in the carcinoma tissues. Surfactant-associated protein A (SP-A) was detected as two bands (a 27-kDa band and a 54-kDa band) in the ultraheavy, heavy, and light surfactant aggregates found in the non-carcinoma tissues. Although both SP-A bands were detected in the heavy and light surfactant aggregates from adenocarcinoma tissues, the 54-kDa band was not detected in squamous cell carcinoma tissues. Liver AP (LAP) was detected in the heavy and light surfactant aggregates from both non-carcinoma and squamous carcinoma tissues, but not in heavy surfactant aggregates from adenocarcinoma tissues. A larger amount of bone type AP (BAP) was found in light surfactant aggregate fractions from squamous cell carcinomas than those from adenocarcinoma tissues or non-carcinoma tissues from patients with either type of cancer. LAP, BAP, and SP-A were identified immunohistochemically in type II pneumocytes from non-carcinoma tissues and adenocarcinoma cells, but no distinct SP-A staining was observed in squamous cell carcinoma tissues. The present study has thus revealed several differences in pulmonary surfactant aggregates and AP isozymes between adenocarcinoma tissue and squamous cell carcinoma tissue.